1. Field of the Invention
The present invention relates to a forming, filling and sealing machine for concurrently forming a standing pouch with a sheet film and filling the pouch with a filling material while carrying the sheet film downward.
2. Description of the Related Art
As a filling and sealing machine for forming a bag with a sheet film and concurrently filling a liquefied or paste filling material with the bag, a vertical type forming, filling and sealing machine has hitherto been known. A vertical type forming, filling and sealing machine comprises a film forming guide for forming the sheet film into a tubular shape, a vertical sealing mechanism for heat sealing an edge of the film into a tubular shape to produce a tubular film, a pair of squeezing rollers for dividing the filling material introduced into the tubular film and downwardly carrying the tubular film with the divided product, and a end sealing mechanism for horizontally heat sealing the unfilled part produced in the tubular film by the rotation of the squeezing rollers and cutting off the sealed part.
As a machine capable of performing high speed heat sealing and obtaining increased seal strength, Japanese Patent Laid-open No. 172403/95 discloses a vertical type forming, filling and sealing machine having a end sealing mechanism which includes a heater bar for heat sealing the unfilled part and a cooling bar for cooling the heat sealed portion. The heater bar and the cooling bar have the ability to successively press the same portion when the film feed is in a stopped state.
On the other hand, there is a package type of standing pouch. As this standing pouch can be displayed in a shop in a self-supported state, it has been widely used recently as a package form replacing plastic cases, bottles or cans.
Making of standing pouches and filling of filling materials are generally performed in separate processes. Specifically, bags are prepared in advance wherein a bottom folded into a W-form and both sides are heat sealed to keep only the top open. Next in the filling process, the prepared bags are taken out one by one, and filled while being conveyed in a horizontal direction. After the filling product has been introduced into the bags from the opening, the top portion is hermetically closed thorough heat sealing.
However, bag making and filling in separate processes fails to increase productivity. A forming, filling and sealing machine for standing pouches has been developed for bag making and filling successively, the machine folding a sheet film in half, conveying the folded film in the horizontal direction, heat sealing the bottom and both sides, introducing the filling material from the top opening of the bag, after cutting the bags one by one, and heat sealing the top of the bag.
The above forming, filling and sealing machine can increase the productivity for standing pouches. However, a new problem is encountered that a large area is required for installation of the machine because the film is carried horizontally in the machine.
Further, there is a risk that dust may enter the bag because the filling material is introduced into the bag from the top opening while the bag is being carried horizontally. Moreover, since the top opening of the bag is heat sealed, it is very difficult to heat seal the bag without air being introduced into the bag. Therefore, in the case of filler products which easily oxidize or rot, such as foods, it is impossible to maintain product quality. Further, if the filling material, such as detergent, produces bubbles when it is introduced into the bag, bubbles may flow out of the opening of the bag during the filling process, thereby making the surface of the bag dirty or bubbles may stick to the portion to be heat sealed, resulting in faulty sealing of the bag.
The vertical type forming, filling and sealing machine is effective in solving these problems. However, since the standing pouch has a thick bottom, how to fabricate this thick bottom is critical in producing a standing pouch by means of the vertical type forming, filling and sealing machine.
Further, although a conventional vertical type forming, filling and sealing machine disclosed in Japanese Patent Laid-open No. 172403/95 is advantageous in the heat sealing rate as well as in the seal strength in the case of producing a pillow type package, it still has plenty of improvement in the production of a standing pouch. Specifically, the bottoms of standing pouches require at a maximum the heat sealing of four layers of film. Reliable heat sealing of the four-layer portion requires a prolonged sealing time, resulting is a decrease in productivity.